Cultured cheese products are nutritionally dense foods containing 10 to 40% digestible lipid and 3 to 4 kcals/g. They are produced by coagulation of raw or processed milk, concentration of the coagulum solids by mechanical processes to express whey and ageing. During ageing complex microbiological and enzymatic development occur to generate flavor and textural characteristics associated with various cheese types. Lipids per se are biochemically considered to be highly reduced substances. Under the anaerobic environment of the ageing process milk lipids do not participate directly as substrates for metabolic events leading to generation of flavor and aroma qualities of the resulting cheese. However, lipids do have an important impact on the partitioning and capture of volatile flavor and aroma components. Lipids further have impact on the textural properties as well as meltability of the resulting cheese product. Therefore in addition to their nutritional contribution, lipids play an important role in the flavor development, organoleptic characteristics and heat responsiveness of cultured cheese products.
The development of reduced calorie cheese products has evolved around lipid replacement strategies based on blending of low fat or fat-free, skim milk cheese with fat substitutes or fat mimetics to enhance organoleptic quality of the skim milk cheese base. These products are designated processed cheeses. Imitation cheeses are blended variations based on partial or total replacement of milk derived protein with alternative protein sources such as those derived from vegetable sources. Natural cheese products are distinguished from blended products in that the isolation and ageing of the coagulum is conducted in situ without adulteration by subsequent blending of other materials.
The very nature of the cheese making process does not lend itself to extraction of lipid from the intermediate or final products of the process. Rather fractionation of the raw material to remove or reduce lipid at the onset is the protocol of commercial interest today. Low fat processed milk products are readily available as starting raw materials for cultured and other processed dairy products. However, cultured cheese products prepared from skim or substantially reduced-fat milk suffer severe deficiencies due to loss of a key organoleptic component which is lipid. The resulting products are inferior in texture, flavor and appearance and have poor meltability. In part these deficiencies are due to enrichment of natural non-lipid composition with attendant enhancement of their specific functionality, but also due to the loss of unique lipid functionality. The result is an imbalance of physical and organoleptic properties associated with the consumer's expectation for performance of a specific cheese product. Therefore a means has long been sought to reduce the caloric content of cultured cheese products yet maintain high organoleptic standards.
In the past two decades interest in fat substitutes has spawned a host of technological developments in alternative materials for replacement of natural lipids in foods; see for example “Fat Mimetics in Low Fat Cheddar Cheese”, J. Food Science, 61 (5) 1267-1270, 1288 (1996). Water and combinations of hydrocolloidal materials, hydrated microparticulated materials based on starch or proteins and synthetic lipids have been reported. All of the above ingredients have been considered as components in low fat or no fat processed cheese products. Specifically, incorporation of structured polyol polyesters such as sucrose polyesters, SPEs, have been reported as highly efficacious, nutritionally unavailable additives for processed cheeses (U.S. Pat. No. 5,585,132).
Insofar as is know, direct substitution of synthetic or organically structured lipids for natural milk lipids prior to coagulation has heretofore not been considered. Such materials are of sufficiently different specific gravity and display such high interfacial tension in milk based fluids that their colloidal dispersions are not stable. This behavior leads to heterogeneous accumulation and phase separation. Therefore, some means of stabilizing the colloidal dispersed lipid state is required. Stabilization components are characterized by the property that they alone or in combination with other components of the system of interest form structured networks throughout the continuous phase. An important aspect of such stabilization is that the physically compartmentalized microdomains are dimensionally similar in size to that of the colloidal material to be physically constrained. Such compartmentalization provides a barrier to translational migration which leads to heterogeneous accumulation and ultimately consolidation of the dispersed lipid domains. Such stabilizer systems may be soluble, interactive polymeric materials which form polymer gels or particulate reticulated material of supracolloidal dimensions which becomes physically entangled to form particle gels. Hybrid combinations of particulate and polymer gel forming components specifically are particularly useful stabilizers in this application.
While known polymer stabilizer systems, for example xanthan gum or quar gum, could be expected to provide maintenance to some degree of a dispersed exogenous colloidal lipid material in a milk matrix, the very mechanism that leads to such phenomena usually prevents effective water removal from the flocculated curd or milk coagulum. This complication is a result of enhanced water immobilization within the capillary and interstitial domains of the dispersed system, a consequence of translational compartmentalization by polymer gels. However, it has now been found that various forms of structurally expanded celluloses can form the basis of a highly effective stabilizer system for synthetic or chemically modified lipids in either natural or reconstituted low/no fat milk bases. Further, these materials allow excellent control of drainage and water removal from the curd enhancing processability. The use of structurally expanded celluloses in the art of cheese making is believed to be new and unique.